Bioacoustics of Decticus verrucivorus

The calling song is quite uniform in most of western Europe, even where there are morphological differences, e.g. f. monspeliensis in southern France (Figs 227, 236, 245) (perhaps now extinct) and f. aprutianus in the Apennines (Figs 228, 237, 246). However, D. v. assiuus Ingrish, Willemse & Heller, which occurs in the high mountains of central Spain, has a markedly differnet song. Two separate accounts are therefore given below. Western Europe generally (Figs 224-228, 233-237, 242-246. Cd 1, track 27) The loud calling song, produced mainly on hot sunny days, consists of a long echeme-sequence, often lasting several (up to 5 or more) minutes, the sound being reminiscent of the loud ticking sound produced by older free-wheeling bicycles. The sequence begins with well-separated echemes, but these are repeated increasing rapidly untily they merge into a dense sequence with an echeme repetiuon rate of about 8-10/s (rarely slower, down to 6/s). Oscillographic analysis shows each echeme to be quite complex, consisiting of four syllables, grouped into two pairs. The initial opening of the fore wings at the beginning of teh echeme usually produces a distinct hemisyllable, which is sometimes quite loud; the remaining hemisyllables are quiet or absent. The first closing hemisyllable is usually quiet and occassionally absent or almost so; the remaining closing hemisyllables usually lasts 12-20 ms (rarely up to 30 ms) with an interval of about 5-10 ms between the two pairs. The second closing hemisyllable of each pair usually follows immediately, the pause between them being no more than 3 ms at most. The whole echeme, including the initial opening hemisyllable, usually lasts about 45-80 ms, but can be as short as 30 ms if the initial opening hemisyllable is absent. The interval between successive echemes, once a constant repetition rate has been reached, is ually 50-100 ms, but can be as short as 25 ms or as long as 150 ms. Males sometimes produce completely isolated echemes, aprticularly early in the day, but these are clearly not a fully developed calling song. D. v. assiduus (Figs 229-232, 238-241, 247-250. CD 1, track 28) The calling song is also loud and also produced in warm, sunny wather, as well as in cooler conditions. Typically it consists of long sequences of short echemes separated byvery brief pauses (Figs 229-231). The sequences begin rather like those of the more typical song of D. veruccivorus, with more widely spaced, short echemes of 3-6 syllables. The gaps between the syllables soon close up to about 50-100 ms and the echemes become longer, sometimes consisting of up to 30 or more syllable,s though varying greatly and often still including some short ones of 3-5 syllables. A sequence of this kind often lasts for several minutes. Sometimes, in cooler conditions, longer echemes are produced, lasting up to 20 s or more without pause (Fig. 232). The echemes differ markedly from those of typical D. verrucivorous in consiting of simple trains of identical, equally spaced syllables and in varying greatly in the number of syllables they contain. The syllable repetion rate is usually 30-40/s in warm sunny weather, but can be as low as 18/s in cooler conditions. Oscillographic analysis shows that opening hemisyllables are usually very quiet or absent and that the closing hemisyllables usually last about 12-15 ms in warm conditions, but up to 25 ms or more when cooler.

Redescription. Male. Stridulatory file with about 62–63 teeth ( Fig. 6f ). Hind femora armed with 3–5 small ventro-posterior spines. Tenth abdominal tergum with an approximate rectangular concavity in middle ( Fig. 4g ). Epiproct tongue-shaped, covered by tenth abdominal tergum, bent down at a angle of 90° at base. Cercus with an enlarged basal tooth in middle. Female. Tegmen extending up to abdominal apex. Measurement (mm). See Table 6 and Table 7 . Song. The calling song consisted of stereotyped chirps with a regular period (367.08±18.75 ms) and duration (182.68±4.74 ms) ( Fig. 7 f–h). Each chirp was comprised of 5 syllable groups ( Fig. 7h ). The frequency ranges from 6 to 22 kHz, and the frequency of main peak is about 16.95 kHz and that of second peak is not significant ( Fig. 7 i–j). The important parameters are listed ( Tab. 3 ).

Redescription. Tegmen brown (or light green in a few specimens), with dark brown or black spots. Stridulatory file with about 69–72 widely-arranged pegs; pegs gradually becoming shorter from proximal two thirds part towards distal end ( Fig. 6h ). Male cercus branched in or near middle. Subgenital plate with a shallow obtuse-angle incision ( Fig. 4h & m ). Female subgenital plate with an approximately circular incision. Notes. Within this subspecies, morphological variation is large. Male tegmina slightly exceed the knees of hind femora or not. Male cerci are bifurcated in middle, or slightly near base or apex. According to length comparison between tegmen and ovipositor, females can be divided into three types . One type possesses long ovipositor, and tegmen reaching middle of ovipositor; The second type possesses long ovipositor, and tegmen reaching ovipositor apex; The third type possesses comparatively short ovipositor and tegmen reaching middle of ovipositor. The cause of the differences are not clear. Measurement (mm). See Table 6 and Table 7 . Song. Each chirp consists of five or six syllables with different amplitudes in different temperature ( Fig. 7 k–m). Compared with D. v. verrucivorus , the syllable number of chirp and the syllable’s structure and situation are different ( Fig. 7 f–o). The important parameters are listed ( Tab. 3 ).

Description. Male ( holotype ) . Lateral lobe of pronotum as high as wide. Tegmen exceeding abdominal apex, with narrow and sharp apices. Stridulatory file with about 73–76 pegs, gradually becoming smaller towards both ends ( Fig. 6d ). Fore and middle femora without spines; fore and middle tibiae with numerous spines on both margins. Hind femora with 2–4 small spines on inter ventro-anterior margin. Tenth abdominal tergum with approximately rectangular central concavity on dorsal surface. Epiproct tongue-shaped, covered by tenth abdominal tergum and bent down at an angle of 90° at base. Cercus branched in middle. Subgenital plate with a shallow obtuse-angle incision ( Fig. 4i & n ). Colour. Generally brown. Face pale yellow, tinged with cyan spots. Disc of pronotum yellowish brown. Tegmen brown with dark spots. Female unknown. Measurement (mm). See Table 6 and Table 7 .

Description Male ( holotype ) . Lateral lobe of pronotum approximately as wide as high. Stridulatory file with about 70–72 widely-arranged teeth, which gradually become smaller at both ends ( Fig. 6f ). Fore and middle femora without spines; hind femur with a few ventro-posterior spines Each tibia with numerous spines on both margins. Epiproct tongue-shaped, covered by tenth abdominal tergum, bent down at a angle of 45°. Cercus branched in middle ( Fig. 4h ). Colour. Generally light green miscellaneous light brown; ventral surface of abdominal segments yellow. Face generally light green. Pronotum pale brown. Tegmen light green, scattered with approximately transparent spots, with light green to brown venations. Fore and middle leg uniformly brown, hind femur brown with light green. Female. Hind femora armed with 3 small ventro-anterior spines. Subgenital plate with a semicircular incision. Measurement (mm). See Table 6 and Table 7 .